On Tue, Feb 27, 2024 at 07:21:42PM -0800, John Hubbard wrote:
> When building the Linux kernel with a distro .config, most or even all
> possible kernel modules are built. This adds up to 4500+ modules, and
> based on my testing, this causes the pahole utility to run out of space,
> which shows up like this (CONFIG_DEBUG_INFO_BTF=y is required in order
> to reproduce this):
>
> LD .tmp_vmlinux.btf
> BTF .btf.vmlinux.bin.o
> Reached the limit of per-CPU variables: 4096
> ...repeated many times...
> Reached the limit of per-CPU variables: 4096
> LD .tmp_vmlinux.kallsyms1
> NM .tmp_vmlinux.kallsyms1.syms
> KSYMS .tmp_vmlinux.kallsyms1.S
> AS .tmp_vmlinux.kallsyms1.S
> LD .tmp_vmlinux.kallsyms2
> NM .tmp_vmlinux.kallsyms2.syms
> KSYMS .tmp_vmlinux.kallsyms2.S
> AS .tmp_vmlinux.kallsyms2.S
> LD vmlinux
> BTFIDS vmlinux
> libbpf: failed to find '.BTF' ELF section in vmlinux
> FAILED: load BTF from vmlinux: No data available
> make[2]: *** [scripts/Makefile.vmlinux:37: vmlinux] Error 255
> make[2]: *** Deleting file 'vmlinux'
> make[1]: *** [/kernel_work/linux-people/Makefile:1162: vmlinux] Error 2
> make: *** [Makefile:240: __sub-make] Error 2
>
> Increasing MAX_PERCPU_VAR_CNT by 10x avoids running out of space, and
> allows the build to succeed.
do you have an actual count of percpu variables for your config?
10x seems a lot to me
this might be a workaround, but we should make encoder->percpu.vars
dynamically allocated like we do for functions
jirka
>
> Signed-off-by: John Hubbard <[email protected]>
> ---
> btf_encoder.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/btf_encoder.c b/btf_encoder.c
> index fd04008..d9f4e80 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -50,7 +50,7 @@ struct elf_function {
> struct btf_encoder_state state;
> };
>
> -#define MAX_PERCPU_VAR_CNT 4096
> +#define MAX_PERCPU_VAR_CNT 40960
>
> struct var_info {
> uint64_t addr;
> --
> 2.44.0
>
>
On 28/02/2024 09:20, Jiri Olsa wrote:
> On Tue, Feb 27, 2024 at 07:21:42PM -0800, John Hubbard wrote:
>> When building the Linux kernel with a distro .config, most or even all
>> possible kernel modules are built. This adds up to 4500+ modules, and
>> based on my testing, this causes the pahole utility to run out of space,
>> which shows up like this (CONFIG_DEBUG_INFO_BTF=y is required in order
>> to reproduce this):
>>
>> LD .tmp_vmlinux.btf
>> BTF .btf.vmlinux.bin.o
>> Reached the limit of per-CPU variables: 4096
>> ...repeated many times...
>> Reached the limit of per-CPU variables: 4096
>> LD .tmp_vmlinux.kallsyms1
>> NM .tmp_vmlinux.kallsyms1.syms
>> KSYMS .tmp_vmlinux.kallsyms1.S
>> AS .tmp_vmlinux.kallsyms1.S
>> LD .tmp_vmlinux.kallsyms2
>> NM .tmp_vmlinux.kallsyms2.syms
>> KSYMS .tmp_vmlinux.kallsyms2.S
>> AS .tmp_vmlinux.kallsyms2.S
>> LD vmlinux
>> BTFIDS vmlinux
>> libbpf: failed to find '.BTF' ELF section in vmlinux
>> FAILED: load BTF from vmlinux: No data available
>> make[2]: *** [scripts/Makefile.vmlinux:37: vmlinux] Error 255
>> make[2]: *** Deleting file 'vmlinux'
>> make[1]: *** [/kernel_work/linux-people/Makefile:1162: vmlinux] Error 2
>> make: *** [Makefile:240: __sub-make] Error 2
>>
>> Increasing MAX_PERCPU_VAR_CNT by 10x avoids running out of space, and
>> allows the build to succeed.
>
> do you have an actual count of percpu variables for your config?
> 10x seems a lot to me
>
> this might be a workaround, but we should make encoder->percpu.vars
> dynamically allocated like we do for functions
>
> jirka
>
Good idea Jiri; John would you mind trying the attached patch? Thanks!
Alan